13PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University

ESSENTIALSOF HUMAN

ANATOMY& PHYSIOLOGY

The Respiratory System

Organs of the Respiratory system

� Nose

� Pharynx

� Larynx

� Trachea

� Bronchi

� Lungs –

alveoli

Figure 13.1

Function of the Respiratory System

� Oversees gas exchanges between the blood

and external environment

� Exchange of gases takes place within the

lungs in the alveoli

� Passageways to the lungs purify, warm, and

humidify the incoming air

The Nose

� The only externally visible part of the respiratory

system

� Air enters the nose through the external nares

(nostrils)

� The interior of the nose consists of a nasal cavity

divided by a nasal septum

Anatomy of the Nasal Cavity

� Olfactory receptors are located in the mucosa

on the superior surface

� The rest of the cavity is lined with respiratory

mucosa

� Moistens air

� Traps incoming foreign particles

� Lateral walls have projections called conchae

� Increases surface area

� Increases air turbulence within the nasal

cavity

� The nasal cavity is separated from the oral

cavity by the palate

� Anterior hard palate (bone)

� Posterior soft palate (muscle)

Paranasal Sinuses

� Cavities within bones surrounding the nasal cavity

� Frontal bone

� Sphenoid bone

� Ethmoid bone

� Maxillary bone

� Function of the sinuses

� Lighten the skull

� Act as resonance chambers for speech

� Produce mucus that drains into the nasal cavity

Pharynx (Throat)

� Muscular passage from nasal cavity to larynx

� Three regions of the pharynx

� Nasopharynx – superior region behind nasal cavity

� Oropharynx – middle region behind mouth

� Laryngopharynx – inferior region attached to larynx

� The oropharynx and laryngopharynx are common passageways for air and food

Structures of the Pharynx

� Auditory tubes enter the nasopharynx

� Tonsils of the pharynx

� Pharyngeal tonsil (adenoids) in the

nasopharynx

� Palatine tonsils in the oropharynx

� Lingual tonsils at the base of the tongue

Larynx (Voice Box)

� Routes air and food into proper channels

� Plays a role in speech

� Made of eight rigid hyaline cartilages and a

spoon-shaped flap of elastic cartilage

(epiglottis)

Structures of the Larynx

� Thyroid cartilage

� Largest hyaline cartilage

� Protrudes anteriorly (Adam’s apple)

� Epiglottis

� Superior opening of the larynx

� Routes food to the larynx and air toward the trachea

� Vocal cords (vocal folds)

� Vibrate with expelled air to create sound (speech)

� Glottis – opening between vocal cords

Trachea (Windpipe)

� Connects larynx with bronchi

� Lined with ciliated mucosa

� Beat continuously in the opposite direction

of incoming air

� Expel mucus loaded with dust and other

debris away from lungs

� Walls are reinforced with C-shaped hyaline

cartilage

Primary Bronchi

� Formed by division of the trachea

� Enters the lung at the hilus

(medial depression)

� Right bronchus is wider, shorter,

and straighter than left

� Bronchi subdivide into smaller

and smaller branches

Lungs

� Occupy most of the thoracic cavity

� Apex is near the clavicle (superior portion)

� Base rests on the diaphragm (inferior

portion)

� Each lung is divided into lobes by fissures

� Left lung – two lobes

� Right lung – three lobes

� Differences in lung and pleural space pressures

keep lungs from collapsing

Coverings of the Lungs

� Pulmonary (visceral) pleura covers the lung

surface

� Parietal pleura lines the walls of the thoracic

cavity

� Pleural fluid fills the area between layers of

pleura to allow gliding

Respiratory Tree Divisions

� Primary bronchi

� Secondary bronchi

� Tertiary bronchi

� Bronchioli

� Terminal bronchioli

Bronchioles

� Smallest branches

of the bronchi

� All but the

smallest branches

have reinforcing

cartilage

� Terminal

bronchioles end

in alveoli

Figure 13.5a

Respiratory Zone

� Structures

� Respiratory bronchioli

� Alveolar duct

� Alveoli

� Site of gas exchange

Alveoli

� Structure of alveoli

� Alveolar duct

� Alveolar sac

� Alveolus

� Gas exchange takes place within the alveoli

in the respiratory membrane

Respiratory Membrane (Air-Blood Barrier)

� Thin squamous epithelial layer lining alveolar

walls

� Pulmonary capillaries cover external surfaces

of alveoli

Gas Exchange

� Gas crosses the respiratory membrane by

diffusion

� Oxygen enters the blood

� Carbon dioxide enters the alveoli

� Macrophages add protection

� Surfactant coats gas-exposed alveolar

surfaces

Events of Respiration

� Pulmonary ventilation – moving air in and out

of the lungs

� External respiration – gas exchange between

pulmonary blood and alveoli

� Respiratory gas transport – transport of

oxygen and carbon dioxide via the

bloodstream

� Internal respiration – gas exchange between

blood and tissue cells in systemic capillaries

Mechanics of Breathing (Pulmonary

Ventilation)� Completely mechanical process

� Depends on volume changes in the thoracic cavity

� Volume changes lead to pressure changes, which lead to the flow of gases to equalize pressure

� Two phases

� Inspiration – flow of air into lung

� Expiration – air leaving lung

Inspiration

� Diaphragm and intercostal muscles contract

� The size of the thoracic cavity increases

� External air is pulled into the lungs due to an

increase in intrapulmonary volume

Expiration

� Largely a passive process which depends on

natural lung elasticity

� As muscles relax, air is pushed out of the

lungs

� Forced expiration can occur mostly by

contracting internal intercostal muscles to

depress the rib cage

Non-respiratory Air Movements

� Can be caused by reflexes or voluntary

actions

� Examples

� Cough and sneeze – clears lungs of debris

� Laughing

� Crying – causes hyperventilation

� Yawn

� Hiccup – caused by spasms of diapragm

Respiratory Volumes and Capacities� Normal breathing moves about 500 ml of air with each

breath (tidal volume [TV])

� Many factors that affect respiratory capacity

� A person’s size

� Sex

� Age

� Physical condition

� Residual volume

� Air remaining in lung after expiration

� About 1200 ml

� Inspiratory reserve volume (IRV)

� Amount of air that can be taken in forcibly

over the tidal volume

� Usually between 2100 and 3200 ml

� Expiratory reserve volume (ERV)

� Amount of air that can be forcibly exhaled

� Approximately 1200 ml

� Vital capacity

� The total amount of exchangeable air

� Vital capacity = TV + IRV + ERV

� Dead space volume

� Air that remains in conducting zone and

never reaches alveoli

� About 150 ml

� Functional volume

� Air that actually reaches the respiratory

zone

� Usually about 350 ml

� Respiratory capacities are measured with a

spirometer

Respiratory Sounds

� Sounds are monitored with a stethoscope

� Bronchial sounds – produced by air rushing

through trachea and bronchi

� Vesicular breathing sounds – soft sounds of

air filling alveoli

External Respiration

� Oxygen movement into the blood

� The alveoli always has more oxygen than

the blood

� Oxygen moves by diffusion towards the

area of lower concentration

� Pulmonary capillary blood gains oxygen

� Carbon dioxide movement out of the blood

� Blood returning from tissues has higher

concentrations of carbon dioxide than air

in the alveoli

� Pulmonary capillary blood gives up carbon

dioxide

� Blood leaving the lungs is oxygen-rich and

carbon dioxide-poor

Gas Transport in the Blood

� Oxygen transport in the blood

� Inside red blood cells attached to hemoglobin

(oxyhemoglobin [HbO2])

� A small amount is carried dissolved in the plasma

� Carbon dioxide transport in the blood

� Most is transported in the plasma as bicarbonate ion

(HCO3–)

� A small amount is carried inside red blood cells on

hemoglobin, but at different binding sites than those

of oxygen

Internal Respiration

� Exchange of gases between blood and body

cells

� An opposite reaction to what occurs in the

lungs

� Carbon dioxide diffuses out of tissue to

blood

� Oxygen diffuses from blood into tissue

Neural Regulation of Respiration

� Activity of respiratory muscles is transmitted to the

brain by the phrenic and intercostal nerves

� Neural centers that control rate and depth are located

in the medulla

� The pons appears to smooth out respiratory rate

� Normal respiratory rate (eupnea) is 12–15

respirations per minute

� Hyperpnia is increased respiratory rate often due to

extra oxygen needs

Factors Influencing Respiratory Rate and

Depth

� Physical factors

� Increased body temperature

� Exercise

� Talking

� Coughing

� Volition (conscious control)

� Emotional factors

� Chemical factors

� Carbon dioxide levels

� Increased carbon dioxide increases respiration

� Changes in carbon dioxide act directly on the

medulla oblongata

� Oxygen levels

� Changes in oxygen concentration in the blood are

detected by chemoreceptors in the aorta and

carotid artery

� Information is sent to the medulla oblongata

Respiratory Disorders: Chronic

Obstructive Pulmonary Disease (COPD)

� Exemplified by chronic bronchitis and emphysema

� Major causes of death and disability in the US

States

� Features of these diseases

� Patients almost always have a history of smoking

� Labored breathing (dyspnea) becomes

progressively more severe

� Coughing and frequent pulmonary infections are

common

� Most victims retain carbon dioxide, are hypoxic

and have respiratory acidosis

� Those infected will ultimately develop

respiratory failure

Emphysema

� Alveoli enlarge as adjacent chambers break

through

� Chronic inflammation promotes lung fibrosis

� Airways collapse during expiration

� Patients use a large amount of energy to exhale

� Over inflation of the lungs leads to a

permanently expanded barrel chest

� Cyanosis appears late in the disease

Chronic Bronchitis

� Mucosa of the lower respiratory passages

becomes severely inflamed

� Mucus production increases

� Pooled mucus impairs ventilation and gas

exchange

� Risk of lung infection increases

� Pneumonia is common

� Hypoxia and cyanosis occur early

Lung Cancer

� Accounts for 1/3 of all cancer deaths in the

United States

� Increased incidence associated with smoking

� Three common types

� Squamous cell carcinoma

� Adenocarcinoma

� Small cell carcinoma

Sudden Infant Death syndrome (SIDS)

� Apparently healthy infant stops breathing and

dies during sleep

� Some cases are thought to be a problem of the

neural respiratory control center

� One third of cases appear to be due to heart

rhythm abnormalities

Asthma

� Chronic inflamed hypersensitive bronchiole

passages

� Response to irritants with dyspnea, coughing,

and wheezing

Developmental Aspects of the

Respiratory System

� Lungs are filled with fluid in the fetus

� Lungs are not fully inflated with air until two

weeks after birth

� Surfactant – lowers alveolar surface tension

� There isn’t a sufficient amount until the

28th week in fetal development

� Premature babies often have trouble

breathing

� Important birth defects

� Cystic fibrosis – over secretion of thick

mucus clogs the respiratory system

� Cleft palate

Aging Effects

� Elasticity of lungs decreases

� Vital capacity decreases

� Blood oxygen levels decrease

� Stimulating effects of carbon dioxide

decreases

� More risks of respiratory tract infection

Respiratory Rate Changes Throughout

Life

� Newborns – 40 to 80 respirations per minute

� Infants – 30 respirations per minute

� Age 5 – 25 respirations per minute

� Adults – 12 to 18 respirations per minute

� Rate often increases somewhat with old age